Pretty Skies through Shaders

Pretty Skies through Shaders
For the full version of Super Sky Sisters I wanted to spend some time making a really cool looking sky backdrop for the action to take place on. The original prototype has a decent looking sky, but I think I whipped it up in under an hour and looking back at it now it looks like crap.

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So I turned to my old friend Photoshop for some advice. I played around with various ways of making a cool looking sky, and I eventually I came back around to using a Gradient Map to manage the colors of a black and white image. If you didn't know, I'm a huge fan of using gradient maps. When it comes to high resolution art I tend to have a lot of trouble with choosing palettes and maintaining that palette through the painting. It's really easy to muddy up the colors if I start eye dropping the wrong parts of the image, and working in high res really makes me miss the amount of control I have over my palette when working with pixel art... but gradient maps are a good band aid for this!

I feel like a broken record with gradient maps so I won't go into too much detail for this post on what they are. To put it simply an image's colors can be remapped to a new set of colors based on lightness. Here's a quick example of what that means.

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So how can I use this for painting skies? By using a gradient map to take care of all the colors all I have to do is paint up something in grayscale first...

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And then I can spend a little time making a nice sky colored gradient...

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Then I can apply that to the image as a gradient map and like some kind of magic my image has awesome colors!

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My idea for the sky at this point was to have one static sky image, and then decorate it with a bunch of varied cloud sprites. The total amount of assets I use for rendering the sky are as follows:

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My first thought at this point was to just apply the gradient map to the asset directly and export it with the blue colors baked in. If I did it that way then I wouldn't need to worry about using any shaders in the game, and I thought that would be the best bet, but I quickly ran into an issue with the color.

It turns out baking a gradient map into an image with alpha has pretty undesirable results. Check out how one of the clouds look when the gradient map is baked in.

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When using these sprites on top of an already baked in sky background I end up getting some colors that are less than ideal. Some parts come out grey and white and black which can look pretty ugly. So I ended up scrapping the whole baked in gradient map idea.

Instead I just exported all of my assets in grayscale and also exported the gradient. I then applied a relatively simple shader just to apply that gradient map to the image. In Otter I'm using a Surface to render the entire sky to. That surface then has the shader along with the gradient texture. The result looks like this:

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It looks incredibly cool in motion, but unfortunately it's tough to show it without a full video recording. There's too many colors going on for a gif to really show how cool it looks.

A cool side effect of using a shader with a real time gradient map application is that I can switch to a different gradient and the sky can be totally different. For example I can take a gradient that looks like this:

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And the sky then looks like this:

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